Air-pressure brake



QJIYJO, 1928. 1,677,033

M v E. KREHANN AIR PnrxssgmlizBRA-1m,I

Filed Nov. 2e, 1927 2f sheets-sheet 1 July 10, 1928.

E. KREHANN .un PRESSURE BRKE 2 sheets-sheet 2 Filed Nov. 28, 1927 fari/7777K' 5./7/re/m1111 Patented July 10, 1928.

Para NAT cierres.

man; KREHKNN, or' VIENNA; AUSTRIA", Assis-Nanos ONE-HALF To" THE FIRM' GE- BRDER HARDY, MAscHINENrAi-:emx Unnernssnnnrnxrmn' GESELLSCHAFT, or

VIENNA; AUSTRIA.

AIR-TRESSURE'` BRAKE.

ApplicationlediNovember 28 1927, Serial No. 236,327, and nfAustriaDecemberY 15; 1926.

This invention relates to an air pressure brake ot that class in which'two pistons ditiering in diameter and moving in opposite directions act insuccession on the link and lever gearing of the brakes,ithe smaller piston acting .tirstbeinglocked in position at theV end of its stroke bya pawl and ratchet gear. According to the invention this pawl and ratchet gear is located in the casing between the two pistons. Thereby not only a very compact structure is secured and more particularly the result is` obtained; that all the parts ofthe paWl vand ratchet gear are protected from injury and dust as also from snow andice by the casing surrounding the same.

The drawings illustrate by `Way of example a constructional form of the invention. Figs 1 `to 3 show theapparatus in the position of release, of a contact and yfully applied position. Fig`4 shows a detail. Figs. 5 and 6 show another' constructional forni and Fig. 7l illustrates a further constructional form-of the brake.`

In `the closed casina` 11 secured to the vehicle frame two coaxialD brake cylinders 38. 39 differing in diamter are provided in which work the pistons'2a`ndf3. The hollow piston` rod 40 of: the piston 2 secured to and preferably made `integral with the saine carries at its end projecting from-the cylinder an elongated slot 41 into which engagesa journal pin ofthe link` and lever gear of the brake. An `alnitment 42 on `the casing 1 serves for holdingthis journal pinin `the release position of the piston 2. The connection of the small piston 43 Withthe link and lever gear is effected by an eye 44 provided in its piston `rod 43 into which eye engages the bolt of the link and lever gearing.

The link and lever gearing ot' the brake consistsoff the levers 1G and 21 carryinglthe bolts `15` and 20 to which leversare pivoted at 17 and 22,` the operatingr links 19 and 24 of the brake shoesbeingvsuspended at 45on the vehicle'frarne. i i i The levers A16 andQl are connected by a link ipivoted` to these levers byibolts` 26, 27 and by aretracting spring28 tending to `return the levers `into the release position.

Each ofthe pistons f2 and 31is actediupon by a spring 4' and 6 respectively. In the case of" the construetional form shown in Figs. 1 to 3 to the large piston a strong spring` 4 and to the small pistoni a weaker 55 spring' 6 is associated.

Air under pressure` enters through any siintableorfpreterred control valve g29anil the channel 30 into the working space of the cylinder 39 connected t'o the working. 60 spacev oi the cylinder 38 by a passage 47 iricluding athree Way cock12.

The piston 3`carries with soinetslight axial play` a-ratchet rack 7 guided in the casing 1 the free endiotsuch rack reaching` intoa tubular ertension 46 fixed in the casing: and p1'o]ect1ng into the: hollov-7 piston? rod"40 of the piston 2. A' pawl 8 pivotedy at' 9 in the casing' 1 and acted upony by a springl() is adapted to engage with this ratchet rack. 70. The pawl 8 is held in its disengaged position by. a` pin `l1 acting on an arm of the y pawl andguided in a borein the Vcasing bv ashoulderor piston 18 mountedthereonantl tightly fitting suchborethe said pinxa'buti 75 ting against the piston 2. The shoulder of the pin might also be replaced by a diaphragm. The by passages 13 and 14` serve orequalizing the pressures'on both sides oi' the pistons Whilein. the release position. so

Fig. 1 shows the apparatus inthe release position. lhen the brakes have tobe ap-` plied air under pressure is admitted-through the control valve `29and'the passage 30 on the front side of the piston 3 moving it to g5 the right together withthe rack 7 against the action of the spring 6 and the resistance-s of the link and, lever gear# Furthern'iore airV under pressure `enters througlitlie passage 47` and the cock 12 atthe front side 90 of the piston 2.` This piston which at one side is constructed in the manner of'a valve and the cylinder head opposite theretocarry circular. ribs 5 which tightly iit each. other as long. as the brakes are released, so that the airiunder pressure iirst acts only onpart'of the pistonisnrface and cannot inove thefpiston againstthe action .ofV the strengl spring 4. The bolt 15 therefore constitutes a stationary fulcruln for the link andlevercgear ot the'brake, Which'owing to the movement of therpiston-B is brought into the position shown in Fig. 2 lin whichuthebrakeshoes-QB are in contactwith the wheel tyreslY In the ineanwhilethe pressure oftllef` air 105 ente1ingthe cylinder 39 and hence alsov act; ing on the central part ofthe piston grad# ua-lly increasesuntil tinalllyitsl pressuieex erted on the front side of the piston increased so far that now the resistance of the spring 4 is overcome and the piston is moved to the left. Owing to the tact that when the ribs 5 come out ot' Contact with each other at this moment the pressure begins to act on the entire surface of the piston and the brake shoes S23 as pressed against the wheels with great force as shown in Fig. 3.

lVhen the piston moves away from its release position it releases the pin 11 and hence also the pawl 8 which latter then engages into the atchet rack and thereby locks thc piston 3 in its position. Therefore during the stroke of the piston 2 the bolt 2O engaging the .piston rod 43 forms the fixed fulcrum of the link and lever gears. The slight lost motion between the rack' 7 and the piston 3 secures the engagement ot' the pawl 8 into the rack 7.

lVhen the brake shoes have to be released the air under pressure is permitted to escape from the working chambers of the cylinders 38 and 39 by the control valve 29 so that the piston 3 being locked in position by the pawl 8, first the piston 2 returns under the action of the spring Il and the elastic lorcesot the deformed link and lever gear. 0n reaching its initial position it pushes the pin 1l to the right andthereby disengages the pawl Seo that then the piston 3 is pushed back by the spring 6, until the parts have resumed their positions shown in Fi g. l.

It' the three way cock 12, establishing communication between the working spaces of the cylinders 38 and 39, is in the position shown `in Fig. 4 it shuts oft the admission of" air under pressure to the piston 2 and connects its working chamber with theatmosphere through thev port'3l. ln this case the brakes are applied only by the small piston This expedient will be made use of in the case of `freight trains which vwhen empty require only a small brake for'ce for the obtention of which the smallpiston is sailicient. It the vehicles are loaded the cock is turned again into the position shown in F ig. 1 and the brakes are applied in the manner above described.

The same arrangen'lent may be used for brakes for express trains the cock being adjusted according to the ruiming speed. Inr this case the cock may be operated autonialically by any one of the well known brake force governors dependent on the speed.

In the constructional Jform shown in Fig. 5 the operative surface of the large piston 2 is madev smooth and aspeeial loaded valve is interposed in the connecting channel 4T of the cylinders 38 and 39. The valve body 32 guided in the easing 1 is movable between two seals 34 and 36 and is acted upon by a spring 33 tending to force itagainst the seat In the position shown in Fig. 5 the admission of air under pressure to the cylin- 2 has der 38 is shut otf and the space in front of the piston 2 is connected to the atmosphere by the port 35. When during the movement ot the brake shoes towards the wheels due to the movement of the piston 3 as above described, the pressure in the channel 47 has snliiciently increased to overcome the resistance of the spring 33, the valve body 32 is moved into the position shown in Fig. 6 in which it opens the admission of air under pressure to the piston 2 which then operates as described.

According to Fig. 7 the valve 32 is located in the control valve 37 itselt` controlling in this case two channels. By one of these channels and the channel 30 air under pressure enters on operating the control valve immediately in front ol the piston 3 while the second channel 48 is opened after the pressure has increased to a certain degree and hence a'ltcr a time sufficient :torlthe small piston 3 to bring the brake shoes into contact with the wheels. i

Finally it is observed that instead of the pawl and ratchet gear also a sell arresting l'rictional escapement gear may be used.

llf'hat I claim is:

l. ln an air pressure brake comprising a casing. two coaxial cylinders, arranged opposite each other in such casing and dillcring in diameter, pistons, one for each cylinder, working in such cylinders and adapted to move in opposite directions, piston rods connected to such pistons, springs arranged and adapted to act on the sides remotest from each other, means for supplying air` under pressure to the ends of the cylinders next to each other, a locking device comprising a ratchet element connected to the smaller piston and a pawl element pivoted in the said casing and adapted to engage into the said ratchet element and means for actuating the said pawl element, the said locking device being arranged between the two pistons.

2. In an air pressure brake coml'n'ising a casing, two coaxial cylinders arrangetl opposite each other in such casing and dill'erinf?.v in diameter, pistons. one for each cylinder, working in such cylinders and adapted to move in opposite directions. a hollow piston rod for the larger cylinder and a piston rod for the smaller c ylinder.` springs arranged and adapted to act on thc sides remotest from each other, means for supplying air under pressure to the ends of the cylinders next to each other, a tubular extension in the casing projecting into the hollow piston rod of the larger cylinder, a pa wl and ratchet gear comprising a ratchet rack connected to the smaller piston and guided in the said tubular extension ot the easing and a pawl pivoted in the said casing and adapted to engage into the said ratchet rack and means for actuating the said pawl.

3. In an air pressure brake comprising a casing, two coaxial cylinders, arranged opposite each other in such casing and di'ering in diameter, pistons, one ttor each cylinder, working in such cylinders and adapted to move in opposite directions, piston rods connected to such pistons, springs arranged and adapted to act on the sides remotest from each other, the spring of the larger piston being stronger than thatof the smaller piston, means for supplying air under pressure to the ends of the Vcylinders next to each other, a pawl andratchet gear comprising a ratchet rack connected to the smaller piston and a pawl pivoted in the said casing and adapted to engage into the said ratchet rack and means for actuating the said pawl, the said pawl and ratchet gear being arranged between the two pistons.

4. In an air pressure brake comprising a casing, two coaxial cylinders, arranged opposite each other in such casing and diifering in diameter, pistons. one foreach cylinder, working in such cylinders `and adapted to move in opposite directions, piston rods connected to such pistons, springs arranged and adapted to act on the sides remotest from each other, means for supplying air under pressure to the ends of the cylinders next to each other, a pawl and ratchet gear sma 1er piston and a pawl pivoted in the said casing and adapted to engage into the said ratchet rack and .means operatively connected to the larger piston for bringing the said pawl into engagement with the ratchet rack whenever the larger piston moves away from the smaller piston, the said pawl and ratchet gear being arranged between the two pistons.

5. In an air pressure brake comprising a casing, two coaxial cylinders, arranged opposite each other in such casing and diifering in diameter, pistons, one for each cylinder, working in such cylinders and adapted to move in opposite directions, piston rods connected to such pistons, springs arranged and adapted to act on the sides remotest from each other, means for supplying air under pressure to the ends ot' the cylinders next to each other-` a pawl and ratchet gear comprising a ratchet rack connected to the smaller piston and a pawl pivoted in the said casing and adapted to engage into the said ratchet rack and a link and lever gearing operatively connected to the larger piston and a load acting on the pawl whereby the pawl engages into the ratchet rack whenever the larger piston moves away from the smaller piston and at other times is disengaged from the ratchet rack, the said pawl and ratchet gear being arranged between the two pistons.

6. In an air pressure brake comprising a casing, two coaxial cylinders, arranged opposite each other in such casing and differing comprising a ratchet rack connected to the in diameter, pistons, one for each cylinder, working in such cylinders and adapted to move in opposite directions, piston rods connected to such pistons, springs arranged and adapted to act on the sides remotest from each other, means for supplying air under pressure to the ends of the cylinders next to each other, such means comprising a shutting off element adapted to shut oft' the supply oi' air 'under pressure to the largerl piston, a locking device comprising a ratchet element connected to the smaller piston and a pawl element pivoted in the said casing and adapted to engage into the said ratchet element and means for actuating the said pawl element, the said locking device being arranged between the two pistons.

7. In an air pressure brake comprising a casing, two coaxial cylinders, arranged opposite each other in such casing and differing in diameter, pistons, one for each cylin der, working in such cylinders and adapted to move in opposite directions, piston rods connected to such pistons, springs arranged and adapted to act on the sides remotest from each other, means for supplying air under pressure to the ends of the cylinders next to each other, such means comprising a shutting oli element adapted to shut oli' the supply of air under pressure to the larger piston, and means for simultaneously connecting the pressure space of the larger cylinder to the atmosphere, a locking device' comprising a ratchet element connected to the smaller piston and a pawl element pivoted in the said casing and adapted to engage into the said ratchet element and means for actuating the said pawl element, the said locking device being arranged between the two pistons.

8. In an air pressure brake comprising a casing, two coaxial cylinders, arranged opposite each other in such casing and diierw ing in diameter, pistons, one `for each cylinder, working in such cylinders and adapted to move in opposite directions, piston rods connected to such pistons, springs arranged and adapted to act on the sides remotest from each other, means for supplying air under pressure to the ends ot' the cylinders next to each other, such means comprising a bore in the casing, a pawl and ratchet gear comprising a ratchet rack connected to the smaller piston and a pawl pivoted in the said casing and adapted to engage into the said ratchet rack and means for actuating the said pawl, such `means comprising apin adapted to reciprocate longitudinally in the said bore and an element adapted to move with the said pin and to tightly close the said bore, the said pawl and ratchet gear being arranged between the two pistons.

In testimony4 whereof I have aflixed my signature.

EMIL KREHANN. 

